Rob Manfred said Monday he is "not confident" that there will be a 2020 season and that "as long as there's no dialogue" with the Major League Baseball Players Association, "that real risk is going to continue."

In a conversation with Mike Greenberg for ESPN's The Return of Sports special, Manfred walked back comments made last week, when he said "unequivocally, we are going to play Major League Baseball this year" and pegged the likelihood at "100 percent."

"I'm not confident. I think there's real risk, and as long as there's no dialogue, that real risk is going to continue," Manfred said.

The chance that there will be no season increased substantially on Monday, when the commissioner's office told the players' association that it will not proceed with a schedule unless the union waives its right to claim that management violated a March agreement between the feuding sides, according to a source.

Manfred said the MLBPA's "decision to end good faith negotiations" and the need for an agreement with the union on health and safety protocols "were really negative in terms of our efforts."

"The owners are 100 percent committed to getting baseball back on the field," Manfred said. "Unfortunately, I can't tell you that I'm 100 percent certain that's gonna happen."

MLBPA executive director Tony Clark issued a statement on Monday in response to Manfred's comments that read, "Players are disgusted that after Rob Manfred unequivocally told Players and fans that there would '100%' be a 2020 season, he has decided to go back on his word and is now threatening to cancel the entire season. Any implication that the Players Association has somehow delayed progress on health and safety protocols is completely false, as Rob has recently acknowledged the parties are 'very, very close.'

"This latest threat is just one more indication that Major League Baseball has been negotiating in bad faith since the beginning. This has always been about extracting additional pay cuts from Players and this is just another day and another bad faith tactic in their ongoing campaign."